Sl harq buffer management for nr vehicular communication

ABSTRACT

Apparatuses, methods, and systems are disclosed for scheduling a sidelink transmission. One apparatus includes a processor and a transceiver that receives a TB on SL resources, where the TB is associated with a SL HARQ process. The processor stores the TB in a HARQ soft buffer and makes available the HARQ soft buffer for new data in response to a predefined trigger.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/869,436 entitled “SL HARQ BUFFER MANAGEMENT FOR NR VEHICULARCOMMUNICATION” and filed on Jul. 1, 2019 for Joachim Loehr, Prateek BasuMallick, Karthikeyan Ganesan, and Ravi Kuchibhotla, which isincorporated herein by reference.

FIELD

The subject matter disclosed herein relates generally to wirelesscommunications and more particularly relates to sidelink HARQ operationand buffer management for NR vehicular communication.

BACKGROUND

The following abbreviations are herewith defined, at least some of whichare referred to within the following description: Third GenerationPartnership Project (“3GPP”), Fifth Generation Core (“5GC”), FifthGeneration System (“5GS”), Authentication, Authorization and Accounting(“AAA”), Access and Mobility Management Function (“AMF”),Positive-Acknowledgment (“ACK”), Application Programming Interface(“API”), Base Station (“B S”), Control Element (“CE”), Core Network(“CN”), Control Plane (“CP”), Dedicated Short Range Communication(“DSRC”), Downlink Control Information (“DCI”), Downlink (“DL”),Discontinuous Transmission (“DTX”), Enhanced Mobile Broadband (“eMBB”),Evolved Node-B (“eNB”), Evolved Packet Core (“EPC”), General PacketRadio Service (“GPRS”), Global System for Mobile Communications (“GSM”),Hybrid Automatic Repeat Request (“HARQ”), Home Subscriber Server(“HSS”), Log Likelihood Ratio (“LLR”), Long Term Evolution (“LTE”),Multiple Access (“MA”), Mobility Management (“MM”), Mobility ManagementEntity (“MME”), Negative-Acknowledgment (“NACK”) or (“NAK”), NewGeneration (5G) Node-B (“gNB”), New Radio (“NR”, a 5G radio accesstechnology; also referred to as “5G NR”), Network Slice SelectionAssistance Information (“NSSAI”), Packet Data Unit (“PDU”, used inconnection with ‘PDU Session’), Physical Broadcast Channel (“PBCH”),Physical Downlink Control Channel (“PDCCH”), Physical Downlink SharedChannel (“PDSCH”), Physical Random Access Channel (“PRACH”), PhysicalUplink Control Channel (“PUCCH”), Physical Uplink Shared Channel(“PUSCH”), Public Land Mobile Network (“PLMN”), Quality of Service(“QoS”), Radio Access Network (“RAN”), Radio Access Technology (“RAT”),Random-Access Channel (“RACH”), Receive (“Rx”), Scheduling Request(“SR”), Shared Channel (“SCH”), Session Management (“SM”), SessionManagement Function (“SMF”), Single Network Slice Selection AssistanceInformation (“S-NSSAI”), System Information Block (“SIB”), TransportBlock (“TB”), Transmit (“Tx”), Unified Data Management (“UDM”), UserData Repository (“UDR”), Uplink Control Information (“UCI”), UserEntity/Equipment (Mobile Terminal) (“UE”), Uplink (“UL”), User Plane(“UP”), Universal Mobile Telecommunications System (“UMTS”),Ultra-reliability and Low-latency Communications (“URLLC”), andWorldwide Interoperability for Microwave Access (“WiMAX”). As usedherein, “HARQ-ACK” may represent collectively the Positive Acknowledge(“ACK”) and the Negative Acknowledge (“NACK”) and DiscontinuousTransmission (“DTX”). ACK means that a TB is correctly received whileNACK (or NAK) means a TB is erroneously received. DTX means that no TBwas detected.

In certain wireless communication systems, V2X communication allowsvehicles to communicate with moving parts of the traffic system aroundthem. Two resource allocation modes are used in LTE V2x communicationwhich are also considered as a baseline for corresponding resourceallocation modes in NR v2x communication. Mode-1 corresponds to a NRnetwork-scheduled V2X communication mode. Mode-2 corresponds to an LTEnetwork-scheduled V2X communication mode. Mode-3 corresponds to a NRUE-scheduled V2X communication mode. Mode-4 corresponds to an LTEUE-scheduled V2X communication mode.

In LTE V2X HARQ operation is limited to blind retransmission without anyHARQ feedback. NR V2X communication may support HARQ feedback signalingfor SL transmission. However, UE behavior for SL HARQ protocol operationfor NR V2X communication is not specified.

BRIEF SUMMARY

Methods for scheduling a sidelink transmission are disclosed.Apparatuses and systems also perform the functions of the methods.

One method of a remote unit, e.g., a UE, for scheduling a sidelinktransmission includes configuring a set of SL LCHs with at least one UuLCH restriction parameter, wherein the SL LCHs communicate data over aPC5 interface. The method includes receiving, via internal process, a SLbuffer status reporting trigger for a first SL LCH and determining thatan UL-SCH resource for a new transmission is available. The methodincludes determining that the at least one Uu LCH restriction parameterof the first SL LCH does not match the uplink transmission parametersassociated with the UL-SCH resources available for the new transmissionand triggering a Scheduling Request to a base unit via a Uu interfacefor PC5 resources.

One method of a remote unit, e.g., a Tx UE, for scheduling a sidelinktransmission includes transmitting a first TB on SL resources using afirst SL mode, where the TB is associated with a first SL HARQ process.The method includes detecting a HARQ protocol error associated with theTB and retransmitting the TB on SL resources using a second SL mode inresponse to the HARQ protocol error.

One method of a remote unit, e.g., a Rx UE, for scheduling a sidelinktransmission includes receiving a TB on SL resources, where the TB isassociated with a SL HARQ process. The method includes storing the TB ina HARQ soft buffer and making available the HARQ soft buffer for newdata in response to a predefined trigger.

One method of a remote unit, e.g., a Rx UE, for scheduling a sidelinktransmission includes receiving a TB on SL resources, where the TB isassociated with predefined number of blind HARQ retransmissions. Themethod includes decoding the TB and determining whether the TB iscorrectly decoded. In response to correctly decoding the TB, the methodincludes sending a positive HARQ acknowledgement prior to a last of theblind HARQ retransmissions. Otherwise, the method includes sending anegative HARQ acknowledgement in response to incorrectly decoding aninitial transmission of the TB and each of the blind HARQretransmissions the TB, where no negative HARQ acknowledgement is sentprior to receiving the last of the blind HARQ retransmissions.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the embodiments briefly described abovewill be rendered by reference to specific embodiments that areillustrated in the appended drawings. Understanding that these drawingsdepict only some embodiments and are not therefore to be considered tobe limiting of scope, the embodiments will be described and explainedwith additional specificity and detail through the use of theaccompanying drawings, in which:

FIG. 1 is a schematic block diagram illustrating one embodiment of awireless communication system for scheduling a sidelink transmission;

FIG. 2 is a diagram illustrating one embodiment of a SR procedure for atransmitting V2X UE;

FIG. 3 is a diagram illustrating one embodiment of a NACK-to-ACK errorin V2X communication;

FIG. 4 is a diagram illustrating one embodiment of a user equipmentapparatus that may be used for scheduling a sidelink transmission;

FIG. 5 is a diagram illustrating one embodiment of a network equipmentapparatus that may be used for scheduling a sidelink transmission;

FIG. 6 is a flowchart diagram illustrating one embodiment of a methodthat may be used for scheduling a sidelink transmission;

FIG. 7 is a flowchart diagram illustrating one embodiment of a methodthat may be used for scheduling a sidelink transmission;

FIG. 8 is a flowchart diagram illustrating one embodiment of a methodthat may be used for scheduling a sidelink transmission; and

FIG. 9 is a flowchart diagram illustrating one embodiment of a methodthat may be used for scheduling a sidelink transmission.

DETAILED DESCRIPTION

As will be appreciated by one skilled in the art, aspects of theembodiments may be embodied as a system, apparatus, method, or programproduct. Accordingly, embodiments may take the form of an entirelyhardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects.

For example, the disclosed embodiments may be implemented as a hardwarecircuit comprising custom very-large-scale integration (“VLSI”) circuitsor gate arrays, off-the-shelf semiconductors such as logic chips,transistors, or other discrete components. The disclosed embodiments mayalso be implemented in programmable hardware devices such as fieldprogrammable gate arrays, programmable array logic, programmable logicdevices, or the like. As another example, the disclosed embodiments mayinclude one or more physical or logical blocks of executable code whichmay, for instance, be organized as an object, procedure, or function.

Furthermore, embodiments may take the form of a program product embodiedin one or more computer readable storage devices storing machinereadable code, computer readable code, and/or program code, referredhereafter as code. The storage devices may be tangible, non-transitory,and/or non-transmission. The storage devices may not embody signals. Ina certain embodiment, the storage devices only employ signals foraccessing code.

Any combination of one or more computer readable medium may be utilized.The computer readable medium may be a computer readable storage medium.The computer readable storage medium may be a storage device storing thecode. The storage device may be, for example, but not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, holographic,micromechanical, or semiconductor system, apparatus, or device, or anysuitable combination of the foregoing.

More specific examples (a non-exhaustive list) of the storage devicewould include the following: an electrical connection having one or morewires, a portable computer diskette, a hard disk, a random-access memory(“RAM”), a read-only memory (“ROM”), an erasable programmable read-onlymemory (“EPROM” or Flash memory), a portable compact disc read-onlymemory (“CD-ROM”), an optical storage device, a magnetic storage device,or any suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium may be any tangible mediumthat can contain or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

Code for carrying out operations for embodiments may be any number oflines and may be written in any combination of one or more programminglanguages including an object-oriented programming language such asPython, Ruby, Java, Smalltalk, C++, or the like, and conventionalprocedural programming languages, such as the “C” programming language,or the like, and/or machine languages such as assembly languages. Thecode may execute entirely on the user's computer, partly on the user'scomputer, as a stand-alone software package, partly on the user'scomputer and partly on a remote computer or entirely on the remotecomputer or server. In the latter scenario, the remote computer may beconnected to the user's computer through any type of network, includinga local area network (“LAN”) or a wide area network (“WAN”), or theconnection may be made to an external computer (for example, through theInternet using an Internet Service Provider).

Furthermore, the described features, structures, or characteristics ofthe embodiments may be combined in any suitable manner. In the followingdescription, numerous specific details are provided, such as examples ofprogramming, software modules, user selections, network transactions,database queries, database structures, hardware modules, hardwarecircuits, hardware chips, etc., to provide a thorough understanding ofembodiments. One skilled in the relevant art will recognize, however,that embodiments may be practiced without one or more of the specificdetails, or with other methods, components, materials, and so forth. Inother instances, well-known structures, materials, or operations are notshown or described in detail to avoid obscuring aspects of anembodiment.

Reference throughout this specification to “one embodiment,” “anembodiment,” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. Thus, appearances of the phrases“in one embodiment,” “in an embodiment,” and similar language throughoutthis specification may, but do not necessarily, all refer to the sameembodiment, but mean “one or more but not all embodiments” unlessexpressly specified otherwise. The terms “including,” “comprising,”“having,” and variations thereof mean “including but not limited to,”unless expressly specified otherwise. An enumerated listing of itemsdoes not imply that any or all of the items are mutually exclusive,unless expressly specified otherwise. The terms “a,” “an,” and “the”also refer to “one or more” unless expressly specified otherwise.

As used herein, a list with a conjunction of “and/or” includes anysingle item in the list or a combination of items in the list. Forexample, a list of A, B and/or C includes only A, only B, only C, acombination of A and B, a combination of B and C, a combination of A andC or a combination of A, B and C. As used herein, a list using theterminology “one or more of” includes any single item in the list or acombination of items in the list. For example, one or more of A, B and Cincludes only A, only B, only C, a combination of A and B, a combinationof B and C, a combination of A and C or a combination of A, B and C. Asused herein, a list using the terminology “one of includes one and onlyone of any single item in the list. For example, “one of A, B and C”includes only A, only B or only C and excludes combinations of A, B andC. As used herein, “a member selected from the group consisting of A, B,and C,” includes one and only one of A, B, or C, and excludescombinations of A, B, and C.” As used herein, “a member selected fromthe group consisting of A, B, and C and combinations thereof” includesonly A, only B, only C, a combination of A and B, a combination of B andC, a combination of A and C or a combination of A, B and C.

Aspects of the embodiments are described below with reference toschematic flowchart diagrams and/or schematic block diagrams of methods,apparatuses, systems, and program products according to embodiments. Itwill be understood that each block of the schematic flowchart diagramsand/or schematic block diagrams, and combinations of blocks in theschematic flowchart diagrams and/or schematic block diagrams, can beimplemented by code. This code may be provided to a processor of ageneral-purpose computer, special purpose computer, or otherprogrammable data processing apparatus to produce a machine, such thatthe instructions, which execute via the processor of the computer orother programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart diagramsand/or block diagrams.

The code may also be stored in a storage device that can direct acomputer, other programmable data processing apparatus, or other devicesto function in a particular manner, such that the instructions stored inthe storage device produce an article of manufacture includinginstructions which implement the function/act specified in the flowchartdiagrams and/or block diagrams.

The code may also be loaded onto a computer, other programmable dataprocessing apparatus, or other devices to cause a series of operationalsteps to be performed on the computer, other programmable apparatus orother devices to produce a computer implemented process such that thecode which execute on the computer or other programmable apparatusprovide processes for implementing the functions/acts specified in theflowchart diagrams and/or block diagrams.

The flowchart diagrams and/or block diagrams in the Figures illustratethe architecture, functionality, and operation of possibleimplementations of apparatuses, systems, methods, and program productsaccording to various embodiments. In this regard, each block in theflowchart diagrams and/or block diagrams may represent a module,segment, or portion of code, which includes one or more executableinstructions of the code for implementing the specified logicalfunction(s).

It should also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order noted in theFigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. Other steps and methods may be conceived that are equivalentin function, logic, or effect to one or more blocks, or portionsthereof, of the illustrated Figures.

Although various arrow types and line types may be employed in theflowchart and/or block diagrams, they are understood not to limit thescope of the corresponding embodiments. Indeed, some arrows or otherconnectors may be used to indicate only the logical flow of the depictedembodiment. For instance, an arrow may indicate a waiting or monitoringperiod of unspecified duration between enumerated steps of the depictedembodiment. It will also be noted that each block of the block diagramsand/or flowchart diagrams, and combinations of blocks in the blockdiagrams and/or flowchart diagrams, can be implemented by specialpurpose hardware-based systems that perform the specified functions oracts, or combinations of special purpose hardware and code.

The description of elements in each figure may refer to elements ofproceeding figures. Like numbers refer to like elements in all figures,including alternate embodiments of like elements.

Generally, the present disclosure describes systems, methods, andapparatus for sidelink HARQ buffer management in NR V2X communication,e.g., of UEs engaged in V2X communication. Mode-3 and Mode-4 supportdirect LTE V2X communications but differ on how they allocate the radioresources. For Mode-3, resources are allocated by the cellular network,e.g., eNB. Mode-4 does not require cellular coverage, and vehicles (UEs)autonomously select their radio resources using a distributed schedulingscheme supported by congestion control mechanisms. Mode-4 is consideredthe baseline mode and represents an alternative to 802.11p or dedicatedshort range communications (DSRC).

Both resource allocation Mode-3 and Mode-4 have been designed to satisfythe latency requirements and accommodate high Doppler spreads and highdensity of vehicles for V2X communications. Here, the maximum allowedlatency varies between 20 and 100 ms, depending on the application.Mode-3 uses the centralized eNB scheduler as mentioned before. Thevehicular UE and eNB use the Uu interface to communicate, e.g., sendingof BSR/SR from the transmitting V2X UE to the eNB and receiving inresponse a SL grant on the PDCCH (DCI).

Mode-4 uses the PC5 interface, which offers direct LTE sidelink (SL)between two vehicular UEs. Mode-4 employs distributed UE scheduling andoperates without infrastructure support, even when the UEs is in eNBcoverage. Note that LTE sidelink resources are shared with the LTEuplink. Both LTE duplexing modes (e.g., time and frequency divisionduplexing) are supported.

As mentioned above, NR V2X design uses LTE V2X operation as a baseline.NR V2X also supports both a centralized scheduling mode (e.g.,network-scheduled) and a distributed scheduling mode (e.g.,UE-scheduled). The two resource allocation modes in NR V2X will bereferred to as resource allocation Mode-1 and Mode-2.

For NR V2X it is assumed that HARQ with HARQ feedback signaling issupported for SL transmissions, e.g., at least for unicast andpotentially for groupcast SL transmission. LTE V2X HARQ operation wasrestricted to blind retransmissions without any HARQ feedback. Thesupport of HARQ operation with HARQ feedback for SL transmission raisesseveral questions on how the sidelink HARQ processes are managedrespectively maintained for the different cast types, i.e., unicast,groupcast and broadcast, and resource allocation modes. In particularthe HARQ operation at the transmitting and receiving V2X UE for a SLtransmission in the presence of protocol errors, e.g., NACK to ACK, DTXto ACK errors due to the erroneous physical layer decoding, needs to bedefined. Furthermore, the UE behavior for cases when the transmittingV2X UE switches the scheduling mode for different HARQ (re)transmissionsof a TB transmitted on the PSSCH needs to be specified.

According to the current NR standard, the HARQ transmission buffer of aUE is controlled by the network by means of the New Data Indicator (NDI)signaled for a given HARQ process within a DCI. For network-controllerHARQ buffer management, if the UE receives a DCI containing an NDI valuewhich is toggled compared to the last received NDI value for the sameHARQ process, then the UE will store another generated TB in thetransmission buffer of this HARQ process and hence delete the previouslystored TB. Because for NR V2X, the Tx UE 310 may share the HARQ bufferof the HARQ processes among Mode-1 and Mode-2 transmissions, thereshould be some upper limit defined for how long a TB is stored in thetransmission of a HARQ process; respectively, it should be specifiedwhen the Tx UE 310 can use a HARQ process for the transmission of a newTB.

The present disclosure outlines several methods for an efficient SL HARQprotocol operation for NR V2X. In particular, the HARQ operation for aSL transmission in the resource allocation Mode-1 is disclosed.Furthermore, the UE behavior for cases when the transmitting V2X UEswitches the cast type for different HARQ (re)transmissions of a TBtransmitted on the PSSCH is disclosed.

In NR Rel-15 LCHs may be configured with logical channel restrictionsparameters like maxPUSCH duration, allowedSCS, allowedServingcell, etc.Those parameter are used during LCP procedure for the mapping of LCHs touplink grants which is also referred to as “LCH mapping restriction”,i.e., only LCHs matching the uplink transmission parameters of an uplinkgrant (SCS, PUSCH duration, etc.) are considered for transmitting datain the corresponding PUSCH transmission. In order to enable efficientscheduling of uplink transmissions by having a closer match of uplinktransmission parameters (including numerology and PUSCH transmissionduration) for the first PUSCH transmission to logical channel (LCH)requirements, NR supports an early indication to the gNB of the type oftraffic on the logical channel(s) triggering the SR, through the use ofmultiple, single-bit SR configurations.

In order to avoid the situation that a SR for a low latency LCH may notbe triggered due to having been allocated a UL-SCH resources with aconsiderable scheduling delay “K2” or a long PUSCH transmissionduration, it was agreed for NR Rel-15 that SR is also triggered forcases when the MAC entity is in possession of an UL-SCH resource thatresults in higher latency or transmission duration. This is specified inTS38.321 by following condition: if the UL-SCH resources available for anew transmission do not meet the LCP mapping restrictions (see subclause5.4.3.1) configured for the logical channel that triggered the BSR.

The present disclosure outlines several methods for efficient schedulingof sidelink transmissions for NR V2X. In particular, the SL LCH have Uurestriction parameters used to handle scheduling requests in theresource allocation Mode-1.

In various embodiments, HARQ operation at the V2X receiver side includesidentifying some maximum time a soft buffer is occupied in order toallow communication with some other V2X UEs (e.g., other vehicles). Inone embodiment, a timer is started at the soft buffer when a TB is firststored there. The timer value may be set according to QoS priorityinformation in the SCI associated with the TB. In certain embodimentsthere is a linkage between the QoS priority and a packet delay budget(PDB). Moreover, the soft buffer may be flushed when an ACK is sent forthe TB stored in the soft buffer. In some embodiments, a TB with ahigher priority indicated in SCI may evict from the soft buffer apreviously stored TB with a lower priority indicated in SCI. In certainembodiments, a maximum number of HARQ (re)transmissions for the TB isindicated in SCI. In certain embodiments, the packet delay budget isindicated in SCI. In certain embodiments, a flag (or other indication)in SCI may indicate whether the associated TB is the last HARQretransmission of the TB.

In various embodiments, sidelink HARQ operation in NR V2X communicationconsiders the PDB for autonomous HARQ retransmission. In someembodiments, a timer defines for how long a UE can perform autonomousHARQ retransmission(s) once HARQ protocol error occurred, e.g., NACK-ACKerror. In certain embodiments, this timer is started (or restarted) whenTB is generated or transmitted or put in HARQ Tx buffer. In certainembodiments, this time is only effective for Mode-2 communications.

In various embodiments, the V2X UE may perform HARQ Tx buffer flushingin order to free HARQ processes for allowing Mode-2 HARQ transmissions.Here, a timer may define when UE can use a HARQ process for new initialHARQ transmissions, i.e., Mode-2 transmissions. In certain embodiments,SL HARQ operation includes stalling of HARQ process which was used byMode-1 HARQ transmission “last packet”. In one embodiment, the DCIindicates flushing of buffer, i.e., DCI includes a “last transmissionattempt” indicator. Further, the Tx UE may consider process as available(Mode-2 new transmissions) upon sending a (real) ACK to gNB.Additionally, the Tx UE may consider process as available if a NACK wassent to gNB and a timer is expired.

In various embodiments, when PDB expires the Tx UE should send ACK togNB (even though packet was not correctly received by Rx UE). In certainembodiments, the Tx UE starts timer when packets arrive in buffer.Additionally, the Tx UE will flush HARQ Tx buffer (at least consider itas available) when the PDB expires.

FIG. 1 depicts a wireless communication system 100 for scheduling asidelink transmission for wireless devices communicating V2X messages125, according to embodiments of the disclosure. In one embodiment, thewireless communication system 100 includes at least one remote unit 105,a radio access network (“RAN”) 120, and a mobile core network 140. TheRAN 120 and the mobile core network 140 form a mobile communicationnetwork. The RAN 120 may be composed of a base unit 110 with which theremote unit 105 communicates using wireless communication links 115.Even though a specific number of remote units 105, base units 110,wireless communication links 115, RANs 120, and mobile core networks 140are depicted in FIG. 1, one of skill in the art will recognize that anynumber of remote units 105, base units 110, wireless communication links115, RANs 120, and mobile core networks 140 may be included in thewireless communication system 100.

In one implementation, the RAN 120 is compliant with the 5G systemspecified in the 3GPP specifications. In another implementation, the RAN120 is compliant with the LTE system specified in the 3GPPspecifications. More generally, however, the wireless communicationsystem 100 may implement some other open or proprietary communicationnetwork, for example WiMAX, among other networks. The present disclosureis not intended to be limited to the implementation of any particularwireless communication system architecture or protocol.

In one embodiment, the remote units 105 may include computing devices,such as desktop computers, laptop computers, personal digital assistants(“PDAs”), tablet computers, smart phones, smart televisions (e.g.,televisions connected to the Internet), smart appliances (e.g.,appliances connected to the Internet), set-top boxes, game consoles,security systems (including security cameras), vehicle on-boardcomputers, network devices (e.g., routers, switches, modems), or thelike. In some embodiments, the remote units 105 include wearabledevices, such as smart watches, fitness bands, optical head-mounteddisplays, or the like. Moreover, the remote units 105 may be referred toas the UEs, subscriber units, mobiles, mobile stations, users,terminals, mobile terminals, fixed terminals, subscriber stations, userterminals, wireless transmit/receive unit (“WTRU”), a device, or byother terminology used in the art.

The remote units 105 may communicate directly with one or more of thebase units 110 in the RAN 120 via uplink (“UL”) and downlink (“DL”)communication signals. Furthermore, the UL and DL communication signalsmay be carried over the wireless communication links 115. Here, the RAN120 is an intermediate network that provides the remote units 105 withaccess to the mobile core network 140.

In some embodiments, the remote units 105 communicate with anapplication server 151 via a network connection with the mobile corenetwork 140. For example, an application 107 (e.g., web browser, mediaclient, telephone/VoIP application) in a remote unit 105 may trigger theremote unit 105 to establish a PDU session (or other data connection)with the mobile core network 140 via the RAN 120. The mobile corenetwork 140 then relays traffic between the remote unit 105 and theapplication server 151 in the packet data network 150 using the PDUsession. Note that the remote unit 105 may establish one or more PDUsessions (or other data connections) with the mobile core network 140.As such, the remote unit 105 may concurrently have at least one PDUsession for communicating with the packet data network 150 and at leastone PDU session for communicating with another data network (not shown).

The base units 110 may be distributed over a geographic region. Incertain embodiments, a base unit 110 may also be referred to as anaccess terminal, an access point, a base, a base station, a Node-B, aneNB, a gNB, a Home Node-B, a relay node, a RAN node, or by any otherterminology used in the art. The base units 110 are generally part of aradio access network (“RAN”), such as the RAN 120, that may include oneor more controllers communicably coupled to one or more correspondingbase units 110. These and other elements of radio access network are notillustrated but are well known generally by those having ordinary skillin the art. The base units 110 connect to the mobile core network 140via the RAN 120.

The base units 110 may serve a number of remote units 105 within aserving area, for example, a cell or a cell sector, via a wirelesscommunication link 115. The base units 110 may communicate directly withone or more of the remote units 105 via communication signals.Generally, the base units 110 transmit DL communication signals to servethe remote units 105 in the time, frequency, and/or spatial domain.Furthermore, the DL communication signals may be carried over thewireless communication links 115. The wireless communication links 115may be any suitable carrier in licensed or unlicensed radio spectrum.The wireless communication links 115 facilitate communication betweenone or more of the remote units 105 and/or one or more of the base units110.

In one embodiment, the mobile core network 140 is a 5G core (“5GC”) orthe evolved packet core (“EPC”), which may be coupled to a packet datanetwork 150, like the Internet and private data networks, among otherdata networks. A remote unit 105 may have a subscription or otheraccount with the mobile core network 140. Each mobile core network 140belongs to a single public land mobile network (“PLMN”). The presentdisclosure is not intended to be limited to the implementation of anyparticular wireless communication system architecture or protocol.

The mobile core network 140 includes several network functions (“NFs”).As depicted, the mobile core network 140 includes multiple user planefunctions (“UPFs”) 145. The mobile core network 140 also includesmultiple control plane functions including, but not limited to, anAccess and Mobility Management Function (“AMF”) 141 that serves the RAN120, a Session Management Function (“SMF”) 143, a Policy ControlFunction (“PCF”) 147, and a Unified Data Management function (“UDM”)149. In certain embodiments, the mobile core network 140 may alsoinclude an Authentication Server Function (“AUSF”), a Unified DataRepository (“UDR”), a Network Repository Function (“NRF”) (used by thevarious NFs to discover and communicate with each other over APIs), orother NFs defined for the 5GC.

In various embodiments, the mobile core network 140 supports differenttypes of mobile data connections and different types of network slices,wherein each mobile data connection utilizes a specific network slice.Here, a “network slice” refers to a portion of the mobile core network140 optimized for a certain traffic type or communication service. Anetwork instance may be identified by a S-NSSAI, while a set of networkslices for which the remote unit 105 is authorized to use is identifiedby NSSAI. In certain embodiments, the various network slices may includeseparate instances of network functions, such as the SMF 143 and UPF145. In some embodiments, the different network slices may share somecommon network functions, such as the AMF 141. The different networkslices are not shown in FIG. 1 for ease of illustration, but theirsupport is assumed.

Although specific numbers and types of network functions are depicted inFIG. 1, one of skill in the art will recognize that any number and typeof network functions may be included in the mobile core network 140.Moreover, where the mobile core network 140 is an EPC, the depictednetwork functions may be replaced with appropriate EPC entities, such asan MME, S-GW, P-GW, HSS, and the like. In certain embodiments, themobile core network 140 may include a AAA server.

While FIG. 1 depicts components of a 5G RAN and a 5G core network, thedescribed embodiments for using a pseudonym for access authenticationover non-3GPP access apply to other types of communication networks andRATs, including IEEE 802.11 variants, GSM, GPRS, UMTS, LTE variants,CDMA 2000, Bluetooth, ZigBee, Sigfoxx, and the like. For example, in an4G/LTE variant involving an EPC, the AMF may be mapped to an MME, theSMF mapped to a control plane portion of a PGW and/or to an MME, the UPFmay be mapped to an SGW and a user plane portion of the PGW, the UDM/UDRmay be mapped to an HSS, etc.

In various embodiments, the remote units 105 may communicate directlywith each other (e.g., device-to-device communication) using V2Xcommunication signals 125. Here, V2X transmissions may occur on V2Xresources. As discussed above, a remote unit 105 may be provided withdifferent V2X communication resources for different V2X modes. Mode-1corresponds to a NR network-scheduled V2X communication mode. Mode-2corresponds to an LTE network-scheduled V2X communication mode. Mode-3corresponds to a NR UE-scheduled V2X communication mode. Mode-4corresponds to an LTE UE-scheduled V2X communication mode.

Moreover, the remote units 105 implement SL HARQ processes for at leastsome data transferred over V2X communication signals 125. In variousembodiments, HARQ operation at the receiving remote unit 105 includesidentifying some maximum time a soft buffer is occupied in order toallow communication with some other V2X remote units 105 (e.g., othervehicles). In one embodiment, a timer is started at the soft buffer whena TB is first stored there. The timer value may be set according to QoSpriority information in the SCI associated with the TB. In certainembodiments there is a linkage between the QoS priority and a packetdelay budget (PDB). Moreover, the soft buffer may be flushed when an ACKis sent for the TB stored in the soft buffer. In some embodiments, a TBwith a higher priority indicated in SCI may evict from the soft buffer apreviously stored TB with a lower priority indicated in SCI. In certainembodiments, a maximum number of HARQ (re)transmissions for the TB isindicated in SCI. In certain embodiments, the packet delay budget isindicated in SCI. In certain embodiments, a flag (or other indication)in SCI may indicate whether the associated TB is the last HARQretransmission of the TB.

In various embodiments, sidelink HARQ operation in NR V2X communicationconsiders the PDB for autonomous HARQ retransmission. In someembodiments, a timer defines for how long a remote unit 105 can performautonomous HARQ retransmission(s) once HARQ protocol error occurred,e.g., NACK-ACK error. In certain embodiments, this timer is started (orrestarted) when TB is generated or transmitted or put in HARQ Tx buffer.In certain embodiments, this time is only effective for Mode-2communications.

In various embodiments, the V2X remote unit 105 may perform HARQ Txbuffer flushing in order to free HARQ processes for allowing Mode-2 HARQtransmissions. Here, a timer may define when remote unit 105 can use aHARQ process for new initial HARQ transmissions, i.e., Mode-2transmissions. In certain embodiments, SL HARQ operation includesstalling of HARQ process which was used by Mode-1 HARQ transmission“last packet”. In one embodiment, the DCI indicates flushing of buffer,i.e., DCI includes a “last transmission attempt” indicator. Further, thetransmitting remote unit 105 may consider a HARQ process as available(Mode-2 new transmissions) upon sending a (real) ACK to the base unit110. Additionally, the transmitting remote unit 105 may consider a HARQprocess as available if a NACK was sent to the base unit 110 and a timeris expired.

In various embodiments, when PDB expires the transmitting remote unit105 should send ACK to the base unit 110 (even though packet was notcorrectly received by the receiving remote unit 105). In certainembodiments, the transmitting remote unit 105 starts timer when packetsarrive in buffer. Additionally, the transmitting remote unit 105 willflush HARQ Tx buffer (at least consider it as available) when the PDBexpires.

In the following descriptions, the term eNB/gNB is used for the basestation but it is replaceable by any other radio access node, e.g., BS,eNB, gNB, AP, NR, etc. Further the operations are described mainly inthe context of 5G NR. However, the proposed solutions/methods are alsoequally applicable to other mobile communication systems supportingserving cells/carriers being configured for Sidelink Communication overPC5 interface.

FIG. 2 depicts a diagram 200 for SL scheduling request (“SR”) triggeringat a UE 205. The UE 205 may be one embodiment of the remote unit 105.The UE 205 supports a Uu interface 210 for communicating with a RAN node(e.g., gNB) and also supports a PC5 interface 215 for communicating withone or more UEs (e.g., V2X UEs). Data generated at the UE 205 may beuplink data destined for the RAN node or may be sidelink data destined,e.g., for a V2X UE. Uplink data is mapped to one or more uplink logicalchannels (“UL LCHs”), while sidelink data is mapped to one or moresidelink logical channels (“SL LCH”). Note that for NR V2X, the SL BSRwhich is transmitted on the PUSCH (Uu) carries information on the SLLCHs. Therefore, according to a first solution, the UE 205 is configuredwith a relation between the SL LCHs and the Uu PUSCH resources.

In the depicted embodiments, the UE 205 supports multiple SL LCHs. Here,it is assumed that the UE 205 is configured with at least a first SL LCH(shown as LCH #1) associated with a first traffic type and a second SLLCH (shown as LCH #2) associated with a second traffic type requiringlow latency. Note that the UE 205 may be configured with additional SLLCHs. Additionally, the UE 205 may be configured with at least one ULLCH. Moreover, the described solutions are also applicable where the UE205 is configured with only one SL LCH. For NR SL Mode-1 operation, theUE 205 sends a SL SR/BSR on the Uu interface to the gNB in order toprovide the gNB with buffer status info necessary for allocatingefficiently SL resources on the PC5 interface.

In some embodiments, the SL LCHs are each configured with Uu LCHrestriction parameters. These Uu LCH restriction parameters are used forNR V2X Mode-1 operation for the triggering of a SL SR when the UE hasUL-SCH resources available for a new transmission. In NR Rel-15 Uu LCHsmay be configured with logical channel restrictions parameters likemaxPUSCH duration, allowedSCS, allow edServingcell, etc. Theseparameters are used during LCP procedure for the mapping of UL LCHs toUplink resource grants. As such, the LCH Uu restriction parameter mayalso be referred to as “LCH mapping restriction”, as only LCHs matchingthe uplink transmission parameters of an uplink grant (SCS, PUSCHduration, etc.) are considered for transmitting data in thecorresponding PUSCH transmission.

In various embodiments of the first solution, a UE operating in NR V2XMode-1 triggers a SR for a SL LCH, e.g., low latency SL LCH (i.e., LCH#2), when the UE 205 has a UL-SCH resource available that results inhigher latency or transmission duration. In other words, the UE 205 maycompare the QoS associated with the SL LCH, i.e., latency (PDB), withthe PUSCH duration, SCS, etc. of the UL-SCH allocation on the Uuinterface. In some embodiments a SL LCH may be configured with Uu LCHrestriction parameters like maxP USCH duration, allowedSCS, etc. UE maycompare the Uu LCH restriction parameter configured for a SL LCH withthe PUSCH duration, SCS, etc. of the UL-SCH allocation on the Uuinterface in order to determine whether to trigger a SR.

Upon detecting (internal) a SL BSR trigger for the first SL LCH (i.e.,associated with normal priority traffic—see block 220), the UE 205transmits a first SL SR to the RAN Node (see messaging 225). The UE 205may receive a corresponding grant (depicted here as a UL grant) for thenormal priority traffic (see messaging 230). The UL grant indicates aUL-SCH resource (i.e., PUSCH resource) at a future time.

Later, upon detecting (internal) a SL BSR trigger for the second LCH(i.e., associated with high priority and/or low latency traffic—seeblock 235), the UE 205 identifies that a UL-SCH resource is available(i.e., PUSCH resource 270). However, as discussed in greater detailbelow, the SL BSR triggered by the second LCH cannot use the UL-SCHresource (e.g., because the UL-SCH resources available for a newtransmission do not meet the LCP mapping restrictions configured for thesecond SL logical channel that triggered the SL BSR) and so transmits asecond SL SR to the RAN Node (see messaging 240). The UE 205 may receivea corresponding grant (depicted here as a UL grant) for the SL BSRtriggered by the high priority traffic (see messaging 245).

In order to avoid the situation that a SL SR for a low latency SL LCHmay not be triggered due to having been allocated a PUSCH resource(i.e., PUSCH resource 270) with a considerable scheduling delay or along PUSCH transmission duration, FIG. 2 shows the UE 205 transmitting aSR triggered by SL LCH #2 even though the UE has UL-SCH resourcesavailable for a new transmission (see messaging 240). While FIG. 2depicts the UL-SCH resource being granted to the UE 205 in response to aSL SR, in other embodiments the UL-SCH resources which the UE 205 hasavailable may be allocated by gNB in response to having received UL SR(for Uu).

In various embodiments of the first solution, SR is triggered for a lowlatency SL LCH (i.e., LCH #2) when the UE 205 has a UL-SCH resourceavailable (i.e., PUSCH resource 270) that results in higher latency ortransmission duration. In other words, the UE 205 may compare the QoSassociated with the SL LCH, i.e., latency (PDB), with the PUSCHduration, SCS, etc. of the UL-SCH allocation on the Uu interface.

In the depicted embodiment, the UE 205 transmits a SL BSR for the secondLCH (see messaging 250) using UL-SCH resource(s) granted in response tothe SL SR 240 for the second LCH. The UE 205 receives a SL grant for thesecond LCH (see messaging 255). Here, the UE 205 prepares a SL TB (seeSL MAC PDU assembly; block 260) and transmits SL data for the second LCHvia the PC5 interface (see messaging 265).

Using the UL-SCH resource granted in response to the SL SR 225 for thefirst LCH, the UE 205 transmits a SL BSR for the first LCH (seemessaging 270). The UE 205 receives a SL grant for the first LCH (seemessaging 275). Again, the UE 205 prepares a SL TB (see SL MAC PDUassembly; block 280) and transmits SL data for the first LCH via the PC5interface (see messaging 285).

In some embodiments of the first solution, the UE 205 is to trigger a SLSR for cases when the UE 205 is scheduled with a PUSCH transmission fora MAC PDU including a SL BSR MAC CE which is scheduled later than thenext PUCCH transmission occasion of the SL SR configuration of a SL LCHthat triggered a SL BSR and if the SL LCH that triggered a BSR isconfigured to send a SR when UE has an UL-SCH allocation. According tothis embodiment, a SL LCH has an associated configuration indicatingwhether SL SR shall be triggered when UL-SCH resource are available fora new transmission. Essentially, only low latency SL LCHs would beconfigured such that SR is triggered even though UL-SCH resources areavailable, i.e., when PUSCH resources carrying the SL BSR are later thanthe next PUCCH transmission occasion for the SL SR.

According to another embodiment of the first solution, a threshold interms of a maximum time is configured for a SL LCH which is used todetermine whether a SL SR shall be triggered for cases when the UE 205has been allocated UL-SCH resources for a new transmission. In case theUL-SCH resources are more than the configured threshold ahead, i.e.,measured from the time point when SL BSR has been triggered (for a lowlatency SL LCH), the UE 205 still triggers the SL SR.

In various embodiments of the first solution, a UE 205 may perform SL SRand RACH in parallel. In NR Rel-15 a scheduling request can betransmitted via a configured SR resources on PUCCH or via the randomaccess procedure. The UE 205 may perform random access procedure and SRprocedure in parallel, i.e., some LCHs may be configured with SRresources on PUCCH some other LCHs may not have configured SR resources.According to Rel-15 specifications, the UE 205 may stop, if any, ongoingRandom Access procedure due to a pending SR which has no valid PUCCHresources configured, which was initiated by MAC entity prior to the MACPDU assembly. Such a Random Access procedure may be stopped when the MACPDU is transmitted using a UL grant other than a UL grant provided byRandom Access Response, and this PDU includes a BSR MAC CE whichcontains buffer status up to (and including) the last event thattriggered a BSR.

According to a further embodiment of the first solution, the UE 205shall not stop any ongoing random access procedure triggered for thepurpose of requesting SL resources, i.e., RACH procedure due to apending SL SR which has no valid PUCCH resources configured, when the UE205 transmits a MAC PDU on UL resources on the Uu interface whichincludes a BSR MAC CE which contains buffer status up to (and including)the last event that triggered a BSR prior to the MAC PDU assembly. Onlyin case a SL BSR MAC CE is included in the MAC PDU which contains the SLbuffer status up to (and including) the last event that triggered a SLBSR prior to the MAC PDU assembly, the UE 205 may stop any ongoingrandom access procedure.

FIG. 3 depicts a signaling flow diagram 300 describing a NACK-to-ACKerror during V2X operation. The signaling flow diagram 300 involves aRAN node 305, a V2X transmitting UE (“Tx UE”) 310, and a V2X receivingUE (“Rx UE”) 315. In the depicted embodiment, the UEs 310-315communicate using V2X Mode-1 (network-scheduled mode).

The RAN node 305 sends a Mode-1 SL grant in DCI (see messaging 320), theMode-1 grant assigning SL resources for the transmission of a firsttransmission block, here “TB1”. As depicted, the grant indicates HARQProcess ID (“HPID”) of ‘1’ and new data indicator (“NDI”) is set to ‘0.’Subsequently, the Tx UE 310 transmits the TB1 using the SL resources andalso transmits Sidelink Control Information (“SCI”) relating to thetransmission of TB1 (see messaging 325).

In the depicted embodiment, the Rx UE 315 does not correctly receive TB1(e.g., due to reception and/or decoding error), and thus sends a SL NACKindicator to the Tx UE 310 (see messaging 330). The Tx UE 310 requestsnew SL resources for retransmission of TB1, e.g., by forwarding the SLNACK (see messaging 335). In the depicted example, there is a controlchannel error on the Uu Interface (between RAN node 305 and Tx UE 310)which results in a NACK-to-ACK error, meaning that the RAN node 305incorrectly interprets the messaging 335 as an ACK.

Initially, the Tx UE 310 is unaware of the NACK-to-ACK error; however,the Tx UE 310 becomes aware of the error when the RAN node 305 sends asecond Mode-1 SL grant in DCI indicating SL resources for an initial(e.g., new) transmission of a second TB (“TB2”, see messaging 340). Asthe Tx UE 310 expects SL resources for a HARQ retransmission butactually receives a DCI indicating SL resources for an initialtransmission, the Tx UE 310 determines that a NACK-to-ACK error occurred(see block 345). Here, the error determination may be based on detectingthat the NDI is toggled in the second SL grant (recall, that NDI istoggled to indicate new data, but is not toggled for retransmission).The error determination may also be based on the different TB sizesbetween TB1 and TB2.

In such embodiments, the Tx UE 310 may autonomously switch to V2X Mode-2communications to make further autonomous HARQ retransmissions of thefirst TB (e.g., TB1) (see block 350). In various embodiments, the Tx UE310 is allowed to perform HARQ retransmissions in V2X Mode-2 for alimited amount of time, as described in further detail below.

According to a second solution, a new timer is used at the Tx UE 310,such timer controlling the time the Tx UE 310 is allowed to perform HARQ(re)transmissions for a Transport Block (e.g., TB1) on the PC5interface. According to one implementation of the second solution, atransmission timer is started when a TB is generated or stored in theHARQ transmission buffer. In some embodiments, the timer value may beset according to the packet delay budget (PDB) of the data contained inthe transport block. In such embodiments, the transmission timer may bereferred to as a “PDB timer.”

While the transmission timer is running the Tx UE 310 is allowed tocarry out HARQ (re)transmissions of the TB, for example in the V2XMode-2 (e.g., with autonomous selection of SL resources). However, whenthe transmission timer expires the Tx UE 310 is not permitted to makeany further HARQ (re)transmission of the TB. In certain embodiments, theTx UE 310 switches back to V2X Mode-1 communication upon expiry of thetimer.

As described above, upon detection of a control channel error, e.g.,NACK-to-ACK error on the Uu interface, the Tx UE 310 which istransmitting a TB in the V2X Mode-1 (centralized scheduling, e.g., bythe RAN node 305), switches instead to the V2X Mode-2 (distributedscheduling mode, e.g., by the Tx UE 310) and makes further autonomousHARQ retransmissions of the same TB as long as the above mentioned timeris running. Such control channel errors may lead to a situation wherethe Tx UE 310 sends an NACK to the RAN node 305 in order to request SLresources for further HARQ retransmission, and receives a DCI that doesnot allocate SL resources for a retransmission, but instead allocated SLresources for an initial HARQ transmission (i.e., of a new TB) becausethe NACK was detected by the RAN node 305 as an ACK. As mentioned above,such a situation may be detected by the unexpected toggling of NDI.

In order to avoid a packet loss in such a situation, the Tx UE 310switches to a UE-scheduled mode (e.g., V2X Mode-2) for the transmissionof this TB and autonomously selects SL resources (e.g., based onsensing) for further HARQ retransmissions, as long as the correspondingtransmission timer is running. In this case, the candidate resourceselection window (i.e., T2) is now set accordingly to the remaining PDBbudget.

The scenario where the Tx UE 310 expects SL resources for a HARQretransmission but actually receives a DCI indicating SL resources foran initial transmission, may also happen in the case that DCI (sent bythe RAN node 305) indicating SL resources for an HARQ retransmission isnot detected by the Tx UE 310, i.e., DCI miss-detection, and thecorresponding DTX on the feedback channel is detected as an ACK by theRAN node 305.

In a variant of the second solution, the Tx UE 310 may use the PDB timeras the upper limit for resource reservations when the Tx UE 310 isconfigured to reserve resources for one or more retransmission. Inanother variant, when the Tx UE 310 transmit the initial SL SR/BSRtransmission to the RAN node 305 requesting SL resource, and it did notreceive any SL resource grant from the RAN node 305. The Tx UE 310,according to this variant, may switch to Mode-2 operation when the SL SRtransmission reaches the configured allowed SR maximum count. In anothercase, if the configured SL SR prohibit timer is longer than the PDB forthat packet, then the Tx UE 310 may switch to Mode-2 operation fortransmitting that packet. In another case, if the Tx UE 310's PRACHfails and if the Tx UE 310 reaches the maximum allowed RACHtransmission, then the Tx UE 310 could switch to Mode-2 operations.

According to a third solution (e.g., for resolving SL control channelerrors), the Tx UE 310 considers a HARQ transmission buffer as availablefor transmission of a new TB after a certain predefined criterion ismet. According to one implementation of the third solution, the Tx UE310 considers the transmission buffer of a HARQ process used for SLtransmissions as available for the transmission of a new TB when a timeris expired, the timer being associated with a TB or the HARQ processwhere the TB is stored in. Such as timer may be referred to as a HARQ Txtimer or, alternatively, a transmission buffer timer.

In one such implementation, the HARQ Tx timer may be started when a TBis stored in the transmission buffer of a HARQ buffer, i.e., wheninitial HARQ transmission is done. The timer value may be set to a valuewhich is related to the packet delay budget (PDB) of the data containedin the TB. As such, this time may indicate an upper bound for the timethat the packet may be delayed between the Tx UE 310 and the Rx UE315(s). Upon expiry of the timer, the Tx UE 310 considers the HARQprocess as available for new initial HARQ transmissions, e.g., Tx UE 310can generate a new TB according to a received SL grant or autonomouslyselected SL grant and store the TB in the HARQ buffer of this HARQprocess.

According to another implementation of the third solution, a Tx UE 310considers the transmission buffer of a HARQ process used for SLtransmissions as available for the transmission of a new TB upon havingsent an ACK to the RAN node 305 for the TB currently stored in thetransmission buffer of that HARQ process (i.e., even though the HARQ Txtimer is not yet expired).

According to another implementation of the third solution, the DCI sentfrom the RAN node 305 to the Tx UE 310 for allocating SL resourcesindicates whether the Tx UE 310 can consider the HARQ process for whichthe SL resources are allocated as available after having made thecorresponding indicated SL transmission.

According to one further aspect of the third solution, the timerassociated with a TB/HARQ process may be set to a value according to thePDB value of the highest priority sidelink logical channel (“SL LCH”)having data within a TB. In an alternative implementation, the value ofthe timer associated with a TB/HARQ process may be set according to theminimum or maximum PDB value of the SL LCHs having data within a TB. Theassumption here is that each SL LCH has some associated PDB value, thuseach packet of a SL LCH is associated with a PDB value.

According to a fourth solution (e.g., for managing SL HARQ buffer), themaximum time the corresponding soft buffer of a HARQ process at a Rx UE315 is occupied by one TB is specified or defined. Note that the “softbuffer” is a buffer storing packets/TBs for HARQ Soft Combining. Inorder to allow further communication on the SL (e.g., PC5 interface)with V2X UEs, the time a TB is stored in a soft buffer may be limited tosome maximum value. It should be noted that a V2X UE may be incommunication with several V2X UEs at the same time, therefore the softbuffer management is an important functionality for NR V2X.

According to one implementation of the fourth solution, a timer isassociated with each HARQ process and, respectively, the correspondingsoft buffer at a V2X Rx UE 315. Such as timer may be referred to as aHARQ Rx timer When the data, e.g., LLR(s), of a new TB is placed/storedat the first time in the soft buffer of an HARQ process, the Rx UE 315starts the corresponding HARQ Tx timer. The Rx UE 315 may try to decodethe data stored in the soft buffer as long as the timer is running andnot expired. At timer expiry, the Rx UE 315 may make the HARQprocess/buffer available for new data, e.g., replace the data in thesoft buffer with some other received data (i.e., data of a different newTB is stored in the soft buffer) or flush the soft buffer.

According to another implementation of the fourth solution, the HARQ Rxtimer value may be set according to the Priority (i.e., QoS) informationsignaled within the SCI for the SL data which is stored in the HARQprocess/soft buffer. In a certain implementation, some linkage betweenthe priority (i.e., QoS) information signaled within the SCI and themaximum tolerable decoding delay of a TB (i.e., corresponding to thetimer value) is configured or specified (hardcoded in thespecifications).

According to another implementation of the fourth solution, the Rx UE315 may flush the soft buffer of a (receiving) HARQ process or,respectively, replace the data stored in a soft buffer with other dataupon a trigger event other than expiry of the HARQ Rx timer. In someembodiments, the trigger event is the sending of an HARQ ACK to the TxUE 310 for the corresponding SL transmission of the TB which was storedin the soft buffer. In other words, the Rx UE 315 may flush the softbuffer or replace the data of the soft buffer once the data/TB stored inthe soft buffer was correctly decoded.

In some embodiments, the trigger event is the receipt of a different TB,which is of higher priority than the data/TB stored in the soft buffer.Accordingly, the Rx UE 315 may replace the data stored in the softbuffer of a HARQ process with some other data, i.e., a different TB,which is of higher priority even though the TB currently stored in thesoft buffer was not yet correctly decoded. For cases when the priorityinformation carried in the SCI accompanying the PSSCH (containing theTB) indicates a higher priority than the priority of the TB currentlystored in a soft buffer and there are no other HARQ processes availablefor the reception of a SL transmission, the Rx UE 315 may pre-empt thedata in a HARQ process with some higher priority SL data.

According to a fifth solution (e.g., for managing SL HARQ buffer), theSidelink Control Information (SCI) accompanying the SL data channelPSSCH may contain an indication which is used by the Rx UE 315 for thesoft buffer management. In one implementation, the SCI indicates themaximum number of HARQ transmissions for a TB. Such information can beused by the Rx UE 315 for managing the soft buffer of the HARQ process.After reception of the last HARQ, transmission of a TB the Rx UE 315 mayuse the HARQ process for some other SL transmission, i.e., replace thedata in the soft buffer with some other received data.

According to an alternative implementation of this fifth solution, theSCI accompanying a PSSCH transmission contains some timing informationindicating the maximum time span for the transmission of thecorresponding TB on the PC5 interface. Such timing information may bederived based on the packet delay budget (PDB). Upon reception of theSCI, the Rx UE 315 may start a timer set to the indicated time value.Upon expiry of the timer the Rx UE 315 may make the soft bufferavailable for new data, e.g., flush the soft buffer and/or replace thedata currently stored in the soft buffer with some other data.

According to a further alternative implementation of this fifthsolution, the SCI accompanying a PSSCH transmission contains a fieldindicating whether this is the last HARQ (re)transmission of a TBtransmitted via the PSSCH. When receiving at the Rx UE 315 a SCIindicating that the corresponding PSSCH carries the last HARQ(re)transmission of the TB, the Rx UE 315 knows to not to expect anyfurther HARQ retransmissions of this TB and, correspondingly, afterattempting to decode the TB, the Rx UE 315 may flush the soft bufferand/or use the HARQ process for some other SL transmission, i.e.,replace the data currently stored in the soft buffer with some otherreceived data.

According to a sixth solution, for cases when the maximum allowedtransmission time is expired the Rx UE 315 transmits an ACK to the Tx UE310 as HARQ feedback for a SL transmission even though the TB was notable to be decoded correctly. Such maximum allowed transmission timemight be related to the packet delay budget associated with the datacontained in the TB. The Rx UE 315 may derive the maximum allowedtransmission delay for a SL transmission from the Layer-1 source ID orthe priority (QoS) information signaled within the SCI accompanying a SLdata transmission on the PSSCH.

According to a seventh solution, the Rx UE 315 only sends HARQ feedbackto the Tx UE 310 for the transmission of a TB after the last HARQ(re)transmission of this TB, i.e., no HARQ feedback is sent for theother earlier HARQ (re)transmission of a TB. This feedback indicates tothe Tx UE 310 whether the TB was correctly decoded (after the last HARQ(re)transmissions) or not. Such behavior is in particular suitable forcases when the Tx UE 310 performs some fixed (i.e., predefined) numberof HARQ (re)transmissions of a SL TB, also referred to as “blind HARQretransmissions,” and the Rx UE 315 is ordered to send some HARQfeedback to the Tx UE 310.

According to some alternative implementation of this seventh solution,the Rx UE 315 sends a HARQ feedback, i.e., ACK, as soon as the TB can becorrectly decoded in order to prevent the Tx UE 310 from makingunnecessary retransmission(s) of this TB. In such a scenario, resourcesfor sending HARQ feedback may be configured for every HARQ transmissionof the TB; however, the Rx UE 315 only sends a HARQ ACK after havingsuccessfully decoded the TB, e.g., also referred to as “early ACK”, orafter the last HARQ (re)transmission of the TB. Note that the HARQfeedback sent after the last HARQ (re)transmission may be either ACK orNACK, depending on the decoding result.

According to an eighth solution, when the Tx UE 310 is being scheduledwith SL resources by the RAN node 305, e.g., using V2X Mode-1, the Tx UE310 may skip the SL transmission on the PC5 interface if some certainpredefined criteria are fulfilled. Here, the Tx UE 310 further sendsback an ACK to the RAN node 305 indicating that no further SL resourcesfor a retransmission are required.

According to one implementation of the eighth solution, the criteria forskipping an SL transmission may be related to the buffer status of theTx UE 310, e.g., where no SL data is available for transmission on thescheduled resources. Such a situation may occur if there is no dataavailable for transmission due to restrictions during LCP or due to thefact that there is no data in the Tx UE 310's buffer awaiting atransmission. To improve radio interface efficiency, the Tx UE 310 skipsthe scheduled transmission, rather than sending padding on the SL insuch case.

Another criterion for skipping a scheduled SL transmission may be thedetection of an error occurring on the control channel, e.g., aNACK-to-ACK error. For example, when the Tx UE 310 may expect SLresource for a retransmission but receives SL resources for a newinitial transmission, the Tx UE 310 may skip the scheduled initial SLtransmission, according to this solution.

According to another implementation of this eighth solution, the Tx UE310 does not send any feedback to the RAN node 305, i.e., DTX, on theconfigured feedback resources upon having skipped the correspondingscheduled SL transmission. Alternatively, the Tx UE 310 may send anexplicit signal to the RAN node 305 indicating that the correspondingscheduled SL transmission was skipped by the Tx UE 310. According to afurther implementation of the eighth solution, the Tx UE 310 may triggera SL BSR in case a SL transmission was skipped in order to provide theRAN node 305 with the latest buffer status.

FIG. 4 depicts a user equipment apparatus 400 that may be used forscheduling a sidelink transmission, according to embodiments of thedisclosure. In various embodiments, the user equipment apparatus 400 isused to implement one or more of the solutions described above. The userequipment apparatus 400 may be one embodiment of the remote unit 105and/or any of the V2X UEs 205, 310, and 315, described above.Furthermore, the user equipment apparatus 400 may include a processor405, a memory 410, an input device 415, an output device 420, and atransceiver 425. In some embodiments, the input device 415 and theoutput device 420 are combined into a single device, such as atouchscreen. In certain embodiments, the user equipment apparatus 400may not include any input device 415 and/or output device 420. Invarious embodiments, the user equipment apparatus 400 may include one ormore of: the processor 405, the memory 410, and the transceiver 425, andmay not include the input device 415 and/or the output device 420.

The processor 405, in one embodiment, may include any known controllercapable of executing computer-readable instructions and/or capable ofperforming logical operations. For example, the processor 405 may be amicrocontroller, a microprocessor, a central processing unit (“CPU”), agraphics processing unit (“GPU”), an auxiliary processing unit, a fieldprogrammable gate array (“FPGA”), or similar programmable controller. Insome embodiments, the processor 405 executes instructions stored in thememory 410 to perform the methods and routines described herein. Theprocessor 405 is communicatively coupled to the memory 410, the inputdevice 415, the output device 420, and the transceiver 425.

In various embodiments, the processor 405 controls the user equipmentapparatus 400 to implement the above described UE behaviors. In someembodiments, the processor 405 receives, via the transceiver 425, aconfiguration for a set of SL LCHs with at least one Uu LCH restrictionparameter, wherein the SL LCHs communicate data over a PC5 interface 215supported by the transceiver 425. The processor 405 receives, viainternal process, a SL buffer status reporting trigger for a first SLLCH and determines that an UL-SCH resource for a new transmission isavailable. The processor 405 determines that the at least one Uu LCHrestriction parameter of the first SL LCH does not match the uplinktransmission parameters associated with the UL-SCH resources availablefor the new transmission and triggers a Scheduling Request (i.e., forthe sidelink buffer status report triggered by the first SL LCH) to abase unit via a Uu interface 210 for PC5 resources.

In some embodiments, the at least one Uu LCH restriction parameterincludes one or more of: maximum PUSCH duration, allowed SCS, andallowed serving cell. In certain embodiments, triggering the SchedulingRequest occurs in response to the processor 405 detecting that theparameter maxPUSCH-Duration configured for the first SL LCH has asmaller value than the PUSCH transmission duration associated with theUL-SCH resource available for the new transmission. In certainembodiments, triggering the Scheduling Request occurs in response to theprocessor 405 detecting that a set of allowed SCS for the first SL LCHdoes not include the SCS associated with the UL-SCH resource availablefor the new transmission.

In some embodiments, the processor 405 receives a time threshold. Insuch embodiments, triggering the Scheduling Request occurs in responseto the processor 405 determining that UL-SCH resource available for thenew transmission are more than the time threshold away in time from thetime the SL buffer status reporting trigger for the first SL LCH isreceived. In certain embodiments, triggering the Scheduling Requestoccurs in response to the processor 405 determining that the UL-SCHresource available for the new transmission are later in time than anext physical uplink control channel transmission occasion for theScheduling Request triggered for the first SL LCH.

In various embodiments, the processor 405 transmits, via the transceiver425, a first TB on SL resources using a first SL mode, where the TB isassociated with a first SL HARQ process. The processor 405 detects aHARQ protocol error associated with the TB and retransmits the TB on SLresources using a second SL mode in response to the HARQ protocol error.

In some embodiments, the processor 405 further initiates a timer uponone of: generation of the TB, initial transmission of the TB, andplacement of the TB in a HARQ transmission buffer, whereinretransmitting the TB on SL resources using the second SL mode occurswhile the timer is not expired. In one embodiment, the timer value isbased on a packet delay budget associated with the TB. In anotherembodiment, the timer value is signaled within SCI accompanying the TB.Here, the timer value included in SCI and used by the Rx UE for HARQbuffer management at receiver side.

In various embodiments, the processor 405 further stores the TB in aHARQ transmission buffer and makes available the HARQ transmissionbuffer for new data in response to a predefined trigger. In someembodiments, making available the HARQ soft buffer for new data includesone or more of: flushing the HARQ soft buffer and replacing data storedin the HARQ soft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQtransmission buffer. In one embodiment, the timer value is based on apacket delay budget associated with the TB. In another embodiment, thetimer value is signaled within SCI accompanying the TB. Here, the timervalue indicated within SCI is used at the Rx UE side.

In certain embodiments, the predefined trigger includes receiving anindication in DCI. In certain embodiments, the predefined triggerincludes sending an ACK corresponding to the TB to a base unit.

In various embodiments, the processor 405 receives, via the transceiver425, a TB on SL resources, where the TB is associated with a SL HARQprocess. The processor 405 stores the TB in a HARQ soft buffer and makesavailable the HARQ soft buffer for new data in response to a predefinedtrigger.

In some embodiments, making available the HARQ soft buffer for new dataincludes one or more of: flushing the HARQ soft buffer and replacingdata stored in the HARQ soft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQsoft buffer. In one embodiment, the length of the timer is based on apacket delay budget associated with the TB. In another embodiment, thelength of the timer is based on some information carried in the SCIaccompanying the TB.

In certain embodiments, the predefined trigger includes sending an ACKcorresponding to the TB to a V2X UE. In certain embodiments, thepredefined trigger includes receiving a second TB having a higherpriority than the TB stored in the HARQ soft buffer.

In various embodiments, the processor 405 receives, via the transceiver425, a TB on SL resources, where the TB is associated with predefinednumber of blind HARQ retransmissions. The processor 405 decodes the TBand determines whether the TB is correctly decoded.

In response to correctly decoding the TB, the processor 405 sends apositive HARQ acknowledgement prior to a last of the blind HARQretransmissions. Otherwise, the processor 405 sends a negative HARQacknowledgement in response to incorrectly decoding an initialtransmission of the TB and each of the blind HARQ retransmissions theTB, where no negative HARQ acknowledgement is sent prior to receivingthe last of the blind HARQ retransmissions.

The memory 410, in one embodiment, is a computer readable storagemedium. In some embodiments, the memory 410 includes volatile computerstorage media. For example, the memory 410 may include a RAM, includingdynamic RAM (“DRAM”), synchronous dynamic RAM (“SDRAM”), and/or staticRAM (“SRAM”). In some embodiments, the memory 410 includes non-volatilecomputer storage media. For example, the memory 410 may include a harddisk drive, a flash memory, or any other suitable non-volatile computerstorage device. In some embodiments, the memory 410 includes bothvolatile and non-volatile computer storage media.

In some embodiments, the memory 410 stores data relating to scheduling asidelink transmission. For example, the memory 410 may store V2Xcommunication resources, HARQ processes, and the like. In certainembodiments, the memory 410 also stores program code and related data,such as an operating system or other controller algorithms operating onthe remote unit 105.

The input device 415, in one embodiment, may include any known computerinput device including a touch panel, a button, a keyboard, a stylus, amicrophone, or the like. In some embodiments, the input device 415 maybe integrated with the output device 420, for example, as a touchscreenor similar touch-sensitive display. In some embodiments, the inputdevice 415 includes a touchscreen such that text may be input using avirtual keyboard displayed on the touchscreen and/or by handwriting onthe touchscreen. In some embodiments, the input device 415 includes twoor more different devices, such as a keyboard and a touch panel.

The output device 420, in one embodiment, is designed to output visual,audible, and/or haptic signals. In some embodiments, the output device420 includes an electronically controllable display or display devicecapable of outputting visual data to a user. For example, the outputdevice 420 may include, but is not limited to, an LCD display, an LEDdisplay, an OLED display, a projector, or similar display device capableof outputting images, text, or the like to a user. As another,non-limiting, example, the output device 420 may include a wearabledisplay separate from, but communicatively coupled to, the rest of theuser equipment apparatus 400, such as a smart watch, smart glasses, aheads-up display, or the like. Further, the output device 420 may be acomponent of a smart phone, a personal digital assistant, a television,a table computer, a notebook (laptop) computer, a personal computer, avehicle dashboard, or the like.

In certain embodiments, the output device 420 includes one or morespeakers for producing sound. For example, the output device 420 mayproduce an audible alert or notification (e.g., a beep or chime). Insome embodiments, the output device 420 includes one or more hapticdevices for producing vibrations, motion, or other haptic feedback. Insome embodiments, all or portions of the output device 420 may beintegrated with the input device 415. For example, the input device 415and output device 420 may form a touchscreen or similar touch-sensitivedisplay. In other embodiments, the output device 420 may be located nearthe input device 415.

The transceiver 425 includes at least transmitter 430 and at least onereceiver 435. One or more transmitters 430 may be used to provide ULcommunication signals to a base unit 110, such as the UL transmissionsdescribed herein. Similarly, one or more receivers 435 may be used toreceive DL communication signals from the base unit 110, as describedherein. Although only one transmitter 430 and one receiver 435 areillustrated, the user equipment apparatus 400 may have any suitablenumber of transmitters 430 and receivers 435. Further, thetransmitter(s) 430 and the receiver(s) 435 may be any suitable type oftransmitters and receivers. In one embodiment, the transceiver 425includes a first transmitter/receiver pair used to communicate with amobile communication network over licensed radio spectrum and a secondtransmitter/receiver pair used to communicate with a mobilecommunication network over unlicensed radio spectrum.

In certain embodiments, the first transmitter/receiver pair used tocommunicate with a mobile communication network over licensed radiospectrum and the second transmitter/receiver pair used to communicatewith a mobile communication network over unlicensed radio spectrum maybe combined into a single transceiver unit, for example a single chipperforming functions for use with both licensed and unlicensed radiospectrum. In some embodiments, the first transmitter/receiver pair andthe second transmitter/receiver pair may share one or more hardwarecomponents. For example, certain transceivers 425, transmitters 430, andreceivers 435 may be implemented as physically separate components thataccess a shared hardware resource and/or software resource, such as forexample, the network interface 440.

In various embodiments, one or more transmitters 430 and/or one or morereceivers 435 may be implemented and/or integrated into a singlehardware component, such as a multi-transceiver chip, asystem-on-a-chip, an ASIC, or other type of hardware component. Incertain embodiments, one or more transmitters 430 and/or one or morereceivers 435 may be implemented and/or integrated into a multi-chipmodule. In some embodiments, other components such as the networkinterface 440 or other hardware components/circuits may be integratedwith any number of transmitters 430 and/or receivers 435 into a singlechip. In such embodiment, the transmitters 430 and receivers 435 may belogically configured as a transceiver 425 that uses one more commoncontrol signals or as modular transmitters 430 and receivers 435implemented in the same hardware chip or in a multi-chip module.

FIG. 5 depicts one embodiment of a network equipment apparatus 500 thatmay be used for selective security protection of user plane traffic,according to embodiments of the disclosure. The network equipmentapparatus 500 may be one embodiment of the base unit 121 and/or the RANnode 305. Furthermore, the network equipment apparatus 500 may include aprocessor 505, a memory 510, an input device 515, an output device 520,a transceiver 525. In some embodiments, the input device 515 and theoutput device 520 are combined into a single device, such as a touchscreen. In certain embodiments, the network equipment apparatus 500 doesnot include any input device 515 and/or output device 520.

As depicted, the transceiver 525 includes at least one transmitter 530and at least one receiver 535. Here, the transceiver 525 communicateswith one or more remote units 105 to provide access to one or morePLMNs. Additionally, the transceiver 525 may support at least onenetwork interface 540. In some embodiments, the transceiver 525 supportsa first interface (e.g., Uu interface) that communicates with a remoteunit (e.g., UE) over an access network, a second interface (e.g., an N2interface) that communicates with control-plane functions (e.g., SMF) ina mobile core network (e.g., a 5GC), and a third interface (e.g., an N3interface) that communicates with a user-plane function (e.g., UPF) inthe mobile core network.

The processor 505, in one embodiment, may include any known controllercapable of executing computer-readable instructions and/or capable ofperforming logical operations. For example, the processor 505 may be amicrocontroller, a microprocessor, a CPU, a GPU, an auxiliary processingunit, a FPGA, or similar programmable controller. In some embodiments,the processor 505 executes instructions stored in the memory 510 toperform the methods and routines described herein. The processor 505 iscommunicatively coupled to the memory 510, the input device 515, theoutput device 520, and the first transceiver 525.

In various embodiments, the processor 505 controls the network equipmentapparatus 500 to implement the above described RAN node behaviors. Insome embodiments, via the transceiver 525 the processor 505 configuresfor a set of SL LCHs with at least one Uu LCH restriction parameter. Incertain embodiments, the processor 505 receives a SR for the SL BSRtriggered by the first SL LCH.

The memory 510, in one embodiment, is a computer readable storagemedium. In some embodiments, the memory 510 includes volatile computerstorage media. For example, the memory 510 may include a RAM, includingDRAM, SDRAM, and/or SRAM. In some embodiments, the memory 510 includesnon-volatile computer storage media. For example, the memory 510 mayinclude a hard disk drive, a flash memory, or any other suitablenon-volatile computer storage device. In some embodiments, the memory510 includes both volatile and non-volatile computer storage media.

In some embodiments, the memory 510 stores data relating to scheduling asidelink transmission, for example storing V2X communication resources,HARQ processes, and the like. In certain embodiments, the memory 510also stores program code and related data, such as an operating system(“OS”) or other controller algorithms operating on the network equipmentapparatus 500 and one or more software applications.

The input device 515, in one embodiment, may include any known computerinput device including a touch panel, a button, a keyboard, a stylus, amicrophone, or the like. In some embodiments, the input device 515 maybe integrated with the output device 520, for example, as a touchscreenor similar touch-sensitive display. In some embodiments, the inputdevice 515 includes a touchscreen such that text may be input using avirtual keyboard displayed on the touchscreen and/or by handwriting onthe touchscreen. In some embodiments, the input device 515 includes twoor more different devices, such as a keyboard and a touch panel.

The output device 520, in one embodiment, may include any knownelectronically controllable display or display device. The output device520 may be designed to output visual, audible, and/or haptic signals. Insome embodiments, the output device 520 includes an electronic displaycapable of outputting visual data to a user. For example, the outputdevice 520 may include, but is not limited to, an LCD display, an LEDdisplay, an OLED display, a projector, or similar display device capableof outputting images, text, or the like to a user. As another,non-limiting, example, the output device 520 may include a wearabledisplay such as a smart watch, smart glasses, a heads-up display, or thelike. Further, the output device 520 may be a component of a smartphone, a personal digital assistant, a television, a table computer, anotebook (laptop) computer, a personal computer, a vehicle dashboard, orthe like.

In certain embodiments, the output device 520 includes one or morespeakers for producing sound. For example, the output device 520 mayproduce an audible alert or notification (e.g., a beep or chime). Insome embodiments, the output device 520 includes one or more hapticdevices for producing vibrations, motion, or other haptic feedback. Insome embodiments, all or portions of the output device 520 may beintegrated with the input device 515. For example, the input device 515and output device 520 may form a touchscreen or similar touch-sensitivedisplay. In other embodiments, all or portions of the output device 520may be located near the input device 515.

As discussed above, the transceiver 525 may communicate with one or moreremote units to provide access to one or more PLMNs. The transceiver 525may also communicate with one or more network functions (e.g., in themobile core network 140). The transceiver 525 operates under the controlof the processor 505 to transmit messages, data, and other signals andalso to receive messages, data, and other signals. For example, theprocessor 505 may selectively activate the transceiver (or portionsthereof) at particular times in order to send and receive messages.

In various embodiments, the transceiver 525 includes at least onetransmitter 530 and at least one receiver 535. One or more transmitters530 may be used to provide DL communication signals to a remote unit105, such as the network-scheduled SL grant according to NR V2X Mode-1,described herein. Similarly, one or more receivers 535 may be used toreceive UL communication signals from the remote unit 105, as describedherein. Although only one transmitter 530 and one receiver 535 areillustrated, the network equipment apparatus 500 may have any suitablenumber of transmitters 530 and receivers 535. Further, thetransmitter(s) 530 and the receiver(s) 535 may be any suitable type oftransmitters and receivers.

In certain embodiments, the transmitter/receiver pair used tocommunicate with a remote unit 105 may be combined into a singletransceiver unit, for example a single chip performing functions for usewith both licensed and unlicensed radio spectrum. In some embodiments,the transmitter/receiver pair may share one or more hardware components.For example, certain transceivers 525, transmitters 530, and receivers535 may be implemented as physically separate components that access ashared hardware resource and/or software resource, such as for example,the network interface 540.

In various embodiments, one or more transmitters 530 and/or one or morereceivers 535 may be implemented and/or integrated into a singlehardware component, such as a multi-transceiver chip, asystem-on-a-chip, an application specific integrated circuit (“ASIC”),or other type of hardware component. In certain embodiments, one or moretransmitters 530 and/or one or more receivers 535 may be implementedand/or integrated into a multi-chip module. In some embodiments, othercomponents such as the network interface 540 or other hardwarecomponents/circuits may be integrated with any number of transmitters530 and/or receivers 535 into a single chip. In such embodiment, thetransmitters 530 and receivers 535 may be logically configured as atransceiver 525 that uses one more common control signals or as modulartransmitters 530 and receivers 535 implemented in the same hardware chipor in a multi-chip module.

FIG. 6 depicts one embodiment of a method 600 for scheduling a sidelinktransmission, according to embodiments of the disclosure. In variousembodiments, the method 600 is performed by a UE, such as the remoteunit 105, the UE 205, the Tx UE 310, and/or the user equipment apparatus400, described above. In some embodiments, the method 600 is performedby a processor, such as a microcontroller, a microprocessor, a CPU, aGPU, an auxiliary processing unit, a FPGA, or the like.

The method 600 begins and configures 605 a set of SL LCHs with at leastone Uu LCH restriction parameter, wherein the SL LCHs communicate dataover a PC5 interface. The method 600 includes receiving 610, viainternal process, a SL buffer status reporting trigger for a first SLLCH. The method 600 includes determining 615 that an UL-SCH resource fora new transmission is available. The method 600 includes determining 620that the at least one Uu LCH restriction parameter of the first SL LCHdoes not match the uplink transmission parameters associated with theUL-SCH resources available for the new transmission. The method 600includes triggering 625 a Scheduling Request to a base unit via a Uuinterface for PC5 resources. The method 600 ends.

FIG. 7 depicts one embodiment of a method 700 for scheduling a sidelinktransmission, according to embodiments of the disclosure. In variousembodiments, the method 700 is performed by a UE, such as the remoteunit 105, the UE 205, the Tx UE 310, and/or the user equipment apparatus400, described above. In some embodiments, the method 700 is performedby a processor, such as a microcontroller, a microprocessor, a CPU, aGPU, an auxiliary processing unit, a FPGA, or the like.

The method 700 begins and transmits 705 a first TB on SL resources usinga first SL mode, where the TB is associated with a first SL HARQprocess. The method 700 includes detecting 710 a HARQ protocol errorassociated with the TB. The method 700 includes retransmitting 715 theTB on SL resources using a second SL mode in response to the HARQprotocol error. The method 700 ends.

FIG. 8 depicts one embodiment of a method 800 for scheduling a sidelinktransmission, according to embodiments of the disclosure. In variousembodiments, the method 800 is performed by a UE, such as the remoteunit 105, the UE 205, the Rx UE 315, and/or the user equipment apparatus400, described above. In some embodiments, the method 800 is performedby a processor, such as a microcontroller, a microprocessor, a CPU, aGPU, an auxiliary processing unit, a FPGA, or the like.

The method 800 begins and receives 805 a TB on SL resources, where theTB is associated with a SL HARQ process. The method 800 includes storing810 the TB in a HARQ soft buffer. The method 800 includes makingavailable 815 the HARQ soft buffer for new data in response to apredefined trigger. The method 800 ends.

FIG. 9 depicts one embodiment of a method 900 for scheduling a sidelinktransmission, according to embodiments of the disclosure. In variousembodiments, the method 900 is performed by a UE, such as the remoteunit 105, the UE 205, the Rx UE 315, and/or the user equipment apparatus400, described above. In some embodiments, the method 900 is performedby a processor, such as a microcontroller, a microprocessor, a CPU, aGPU, an auxiliary processing unit, a FPGA, or the like.

The method 900 begins and receives 905 a TB on SL resources, where theTB is associated with predefined number of blind HARQ retransmissions.The method 900 includes decoding 910 the TB and determining 915 whetherthe TB is correctly decoded.

In response to correctly decoding the TB, the method 900 includessending 920 a positive HARQ acknowledgement prior to a last of the blindHARQ retransmissions. Otherwise, the method 900 includes sending 925 anegative HARQ acknowledgement in response to incorrectly decoding aninitial transmission of the TB and each of the blind HARQretransmissions the TB, where no negative HARQ acknowledgement is sentprior to receiving the last of the blind HARQ retransmissions. Themethod 900 ends.

Disclosed herein is a first apparatus for scheduling a sidelinktransmission, according to embodiments of the disclosure. The firstapparatus may be implemented by a UE, such as the remote unit 105, theUE 205, the Tx UE 310, and/or the user equipment apparatus 400. Thefirst apparatus includes a processor and a transceiver that receives aconfiguration for a set of SL LCHs with at least one Uu LCH restrictionparameter, wherein the SL LCHs communicate data over a PC5 interfacesupported by the transceiver. The processor receives, via internalprocess, a SL buffer status reporting trigger for a first SL LCH anddetermines that an UL-SCH resource for a new transmission is available.The processor determines that the at least one Uu LCH restrictionparameter of the first SL LCH does not match the uplink transmissionparameters associated with the UL-SCH resources available for the newtransmission and triggers a Scheduling Request to a base unit via a Uuinterface for PC5 resources.

In some embodiments, the at least one Uu LCH restriction parameterincludes one or more of: maximum PUSCH duration, allowed SCS, andallowed serving cell. In certain embodiments, triggering the SchedulingRequest occurs in response to the processor detecting that the parametermaxPUSCH-Duration configured for the first SL LCH has a smaller valuethan the PUSCH transmission duration associated with the UL-SCH resourceavailable for the new transmission. In certain embodiments, triggeringthe Scheduling Request occurs in response to the processor detectingthat a set of allowed SCS for the first SL LCH does not include the SCSassociated with the UL-SCH resource available for the new transmission.

In some embodiments, the processor receives a time threshold. In suchembodiments, triggering the Scheduling Request occurs in response to theprocessor determining that UL-SCH resource available for the newtransmission are more than the time threshold away in time from the timethe SL buffer status reporting trigger for the first SL LCH is received.In certain embodiments, triggering the Scheduling Request occurs inresponse to the processor determining that the UL-SCH resource availablefor the new transmission are later in time than a next physical uplinkcontrol channel transmission occasion for the Scheduling Requesttriggered for the first SL LCH.

Disclosed herein is a first method for scheduling a sidelinktransmission, according to embodiments of the disclosure. The firstmethod may be performed by a UE, such as the remote unit 105, the UE205, the Tx UE 310, and/or the user equipment apparatus 400. The firstmethod includes configuring a set of SL LCHs with at least one Uu LCHrestriction parameter, wherein the SL LCHs communicate data over a PC5interface. The first method includes receiving, via internal process, aSL buffer status reporting trigger for a first SL LCH and determiningthat an UL-SCH resource for a new transmission is available. The firstmethod includes determining that the at least one Uu LCH restrictionparameter of the first SL LCH does not match the uplink transmissionparameters associated with the UL-SCH resources available for the newtransmission and triggering a Scheduling Request to a base unit via a Uuinterface for PC5 resources.

In some embodiments, the at least one Uu LCH restriction parameterincludes one or more of: maximum PUSCH duration, allowed SCS, andallowed serving cell. In certain embodiments, triggering the SchedulingRequest occurs in response to detecting that the parametermaxPUSCH-Duration configured for the first SL LCH has a smaller valuethan the PUSCH transmission duration associated with the UL-SCH resourceavailable for the new transmission. In certain embodiments, triggeringthe Scheduling Request occurs in response to detecting that a set ofallowed SCS for the first SL LCH does not include the SCS associatedwith the UL-SCH resource available for the new transmission.

In some embodiments, the first method includes receiving a timethreshold. In such embodiments, triggering the Scheduling Request occursin response to determining that UL-SCH resource available for the newtransmission are more than the time threshold away in time from the timethe SL buffer status reporting trigger for the first SL LCH is received.In certain embodiments, triggering the Scheduling Request occurs inresponse to determining that the UL-SCH resource available for the newtransmission are later in time than a next physical uplink controlchannel transmission occasion for the Scheduling Request triggered forthe first SL LCH.

Disclosed herein is a second apparatus for scheduling a sidelinktransmission, according to embodiments of the disclosure. The secondapparatus may be implemented by a UE, such as the remote unit 105, theUE 205, the Tx UE 310, and/or the user equipment apparatus 400. Thesecond apparatus includes a processor and a transceiver that transmits afirst TB on SL resources using a first SL mode, where the TB isassociated with a first SL HARQ process. The processor detects a HARQprotocol error associated with the TB and retransmits the TB on SLresources using a second SL mode in response to the HARQ protocol error.

In some embodiments, the processor further initiates a timer upon oneof: generation of the TB, initial transmission of the TB, and placementof the TB in a HARQ transmission buffer, wherein retransmitting the TBon SL resources using the second SL mode occurs while the timer is notexpired. In one embodiment, the timer value is based on a packet delaybudget associated with the TB. In another embodiment, the timer value issignaled within SCI accompanying the TB.

In various embodiments, the processor further stores the TB in a HARQtransmission buffer and makes available the HARQ transmission buffer fornew data in response to a predefined trigger. In some embodiments,making available the HARQ soft buffer for new data includes one or moreof: flushing the HARQ soft buffer and replacing data stored in the HARQsoft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQtransmission buffer. In one embodiment, the timer value is based on apacket delay budget associated with the TB. In another embodiment, thetimer value is signaled within SCI accompanying the TB.

In certain embodiments, the predefined trigger includes receiving anindication in DCI. In certain embodiments, the predefined triggerincludes sending an ACK corresponding to the TB to a base unit.

Disclosed herein is a second method for scheduling a sidelinktransmission, according to embodiments of the disclosure. The secondmethod may be performed by a UE, such as the remote unit 105, the UE205, the Tx UE 310, and/or the user equipment apparatus 400. The secondmethod includes transmitting a first TB on SL resources using a first SLmode, where the TB is associated with a first SL HARQ process. Thesecond method includes detecting a HARQ protocol error associated withthe TB and retransmitting the TB on SL resources using a second SL modein response to the HARQ protocol error.

In some embodiments, the second method includes initiating a timer uponone of: generation of the TB, initial transmission of the TB, andplacement of the TB in a HARQ transmission buffer, whereinretransmitting the TB on SL resources using a second SL mode occurswhile the timer is not expired. In one embodiment, the timer value isbased on a packet delay budget associated with the TB. In anotherembodiment, the timer value is signaled within SCI accompanying the TB.

In various embodiments, the second method further includes storing theTB in a HARQ transmission buffer and making available the HARQtransmission buffer for new data in response to a predefined trigger. Insome embodiments, making available the HARQ soft buffer for new dataincludes one or more of: flushing the HARQ soft buffer and replacingdata stored in the HARQ soft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQtransmission buffer. In one embodiment, the timer value is based on apacket delay budget associated with the TB. In another embodiment, thetimer value is signaled within SCI accompanying the TB.

In certain embodiments, the predefined trigger includes receiving anindication in DCI. In certain embodiments, the predefined triggerincludes sending an ACK corresponding to the TB to a base unit.

Disclosed herein is a third apparatus for scheduling a sidelinktransmission, according to embodiments of the disclosure. The thirdapparatus may be implemented by a UE, such as the remote unit 105, theUE 205, the Rx UE 315, and/or the user equipment apparatus 400. Thethird apparatus includes a processor and a transceiver that receives aTB on SL resources, where the TB is associated with a SL HARQ process.The processor stores the TB in a HARQ soft buffer and makes availablethe HARQ soft buffer for new data in response to a predefined trigger.

In some embodiments, making available the HARQ soft buffer for new dataincludes one or more of: flushing the HARQ soft buffer and replacingdata stored in the HARQ soft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQsoft buffer. In one embodiment, the length of the timer is based on apacket delay budget associated with the TB. In another embodiment, thelength of the timer is based on some information carried in the SCIaccompanying the TB.

In certain embodiments, the predefined trigger includes sending an ACKcorresponding to the TB to a V2X UE. In certain embodiments, thepredefined trigger includes receiving a second TB having a higherpriority than the TB stored in the HARQ soft buffer.

Disclosed herein is a third method for scheduling a sidelinktransmission, according to embodiments of the disclosure. The thirdmethod may be performed by a UE, such as the remote unit 105, the UE205, the Rx UE 315, and/or the user equipment apparatus 400. The thirdmethod includes receiving a TB on SL resources, where the TB isassociated with a SL HARQ process. The third method includes storing theTB in a HARQ soft buffer and making available the HARQ soft buffer fornew data in response to a predefined trigger.

In some embodiments, making available the HARQ soft buffer for new dataincludes one or more of: flushing the HARQ soft buffer and replacingdata stored in the HARQ soft buffer with new data.

In certain embodiments, the predefined trigger is the expiry of a timer,wherein the timer is initiated in response to storing the TB in the HARQsoft buffer. In one embodiment, the length of the timer is based on apacket delay budget associated with the TB. In another embodiment, thelength of the timer is based on some information carried in the SCIaccompanying the TB.

In certain embodiments, the predefined trigger includes sending an ACKcorresponding to the TB to a V2X UE. In certain embodiments, thepredefined trigger includes receiving a second TB having a higherpriority than the TB stored in the HARQ soft buffer.

Disclosed herein is a fourth apparatus for scheduling a sidelinktransmission, according to embodiments of the disclosure. The fourthapparatus may be implemented by a UE, such as the remote unit 105, theUE 205, the Rx UE 315, and/or the user equipment apparatus 400. Thefourth apparatus includes a processor and a transceiver that receives aTB on SL resources, where the TB is associated with predefined number ofblind HARQ retransmissions. The processor decodes the TB and determineswhether the TB is correctly decoded.

In response to correctly decoding the TB, the processor sends a positiveHARQ acknowledgement prior to a last of the blind HARQ retransmissions.Otherwise, the processor sends a negative HARQ acknowledgement inresponse to incorrectly decoding an initial transmission of the TB andeach of the blind HARQ retransmissions the TB, where no negative HARQacknowledgement is sent prior to receiving the last of the blind HARQretransmissions.

Disclosed herein is a fourth method for scheduling a sidelinktransmission, according to embodiments of the disclosure. The fourthmethod may be performed by a UE, such as the remote unit 105, the UE205, the Rx UE 315, and/or the user equipment apparatus 400. The fourthmethod includes receiving a TB on SL resources, where the TB isassociated with predefined number of blind HARQ retransmissions. Thefourth method includes decoding the TB and determining whether the TB iscorrectly decoded.

In response to correctly decoding the TB, the fourth method includessending a positive HARQ acknowledgement prior to a last of the blindHARQ retransmissions. Otherwise, the fourth method includes sending anegative HARQ acknowledgement in response to incorrectly decoding aninitial transmission of the TB and each of the blind HARQretransmissions the TB, where no negative HARQ acknowledgement is sentprior to receiving the last of the blind HARQ retransmissions.

Embodiments may be practiced in other specific forms. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method of a remote unit comprising: configuring a set of sidelink(“SL”) logical channels (“LCHs”) with at least one Uu LCH restrictionparameter, wherein the SL LCHs communicate data over a PC5 interface;receiving, via internal process, a sidelink buffer status reportingtrigger for a first SL LCH; determining that an uplink shared channel(“UL-SCH”) resource for a new transmission is available; determiningthat the at least one Uu LCH restriction parameter of the first SL LCHdoes not match the uplink transmission parameters associated with theUL-SCH resources available for the new transmission; and triggering aScheduling Request to a base unit via a Uu interface for PC5 resources.2. The method of claim 1, wherein the at least one Uu LCH restrictionparameter comprises one or more of: maximum physical uplink sharedchannel duration, allowed subcarrier spacing, and allowed serving cell.3. The method of claim 1, wherein triggering the Scheduling Requestoccurs in response to detecting that a first parameter maxPUSCH-Durationconfigured for the first SL LCH has a smaller value than the PUSCHtransmission duration associated with the UL-SCH resource available forthe new transmission.
 4. The method of claim 1, wherein triggering theScheduling Request occurs in response to detecting that a set of allowedSubcarrier Spacing for the first SL LCH does not include the SubcarrierSpacing associated with the UL-SCH resource available for the newtransmission.
 5. The method of claim 1, wherein triggering theScheduling Request occurs in response to determining that the UL-SCHresource available for the new transmission are later in time than anext physical uplink control channel transmission occasion for theScheduling Request triggered for the first SL LCH.
 6. The method ofclaim 1, further comprising receiving a time threshold, whereintriggering the Scheduling Request occurs in response to determining thatUL-SCH resource available for the new transmission are more than thetime threshold away in time from the time the sidelink buffer statusreporting trigger for the first SL LCH is received.
 7. A method of aremote unit comprising: transmitting a first transmission block (“TB”)on sidelink (“SL”) resources using a first SL mode, where the TB isassociated with a first SL hybrid automatic repeat request (“HARQ”)process; detecting a HARQ protocol error associated with the TB; andretransmitting the TB on SL resources using a second SL mode in responseto the HARQ protocol error.
 8. The method of claim 7, further comprisinginitiating a timer upon one of: generation of the TB, initialtransmission of the TB, and placement of the TB in a HARQ transmissionbuffer, wherein retransmitting the TB on SL resources using a second SLmode occurs while the timer is not expired.
 9. The method of claim 8,wherein the timer value is based on a packet delay budget associatedwith the TB.
 10. The method of claim 7, further comprising: storing theTB in a HARQ transmission buffer; and making available the HARQtransmission buffer for new data in response to a predefined trigger.11. The method of claim 10, wherein the predefined trigger comprisesexpiry of a timer, wherein the timer is initiated in response to storingthe TB in the HARQ transmission buffer.
 12. The method of claim 11,wherein the timer value is based on a packet delay budget associatedwith the TB.
 13. The method of claim 10, wherein the predefined triggercomprises one of: receiving an indication in downlink controlinformation and sending an ACK corresponding to the TB to a base unit.14. The method of claim 10, wherein making available the HARQ softbuffer for new data comprises one of: flushing the HARQ soft buffer, andreplacing data stored in the HARQ soft buffer with new data.
 15. Amethod of a remote unit comprising: receiving a transmission block(“TB”) on sidelink (“SL”) resources, where the TB is associated with aSL HARQ process; storing the TB in a HARQ soft buffer; and makingavailable the HARQ soft buffer for new data in response to a predefinedtrigger.
 16. The method of claim 15, wherein making available the HARQsoft buffer for new data comprises one of: flushing the HARQ softbuffer, and replacing data stored in the HARQ soft buffer with new data.17. The method of claim 15, wherein the predefined trigger comprisesexpiry of a timer, wherein the timer is initiated in response to storingthe TB in the HARQ soft buffer.
 18. The method of claim 17, wherein thelength of the timer is based on at least one of: a packet delay budgetassociated with the TB, and some information carried in the SidelinkControl information accompanying the TB.
 19. The method of claim 15,wherein the predefined trigger comprises one of: sending an ACKcorresponding to the TB to a V2X UE and receiving a second TB having ahigher priority than the TB stored in the HARQ soft buffer.
 20. A methodof a remote unit comprising: receiving a transmission block (“TB”) onsidelink (“SL”) resources, where the TB is associated with predefinednumber of blind HARQ retransmissions; decoding the TB; determiningwhether the TB is correctly decoded; sending a positive HARQacknowledgement prior to a last of the blind HARQ retransmissions inresponse to correctly decoding the TB; and sending a negative HARQacknowledgement in response to incorrectly decoding an initialtransmission of the TB and each of the blind HARQ retransmissions theTB, wherein no negative HARQ acknowledgement is sent prior to receivingthe last of the blind HARQ retransmissions.